Method and apparatus for separating materials of different specific gravities



April 12, 1932. -r M CHANCE 1,854,107

METHOD AND APPARATUS FOR SEPARATING MATERIALS OF DIFFERENT SPECIFIC GRAVITIES Filed Sept. 30. 1927 Wnessw: Int/elder- Patented Apr. 12, 1932 UNITED STATES PATENT OFFICE THOMAS M. CHANCE, OF MERION', PENNSYLVANIA METHOD AN D APPARATUS FOR SEPABATING MATERIALS 0] DIFFERENT SPECIFIC GBAVITIES Application filed September 30, 1927. Serial No. 223,059.

My invention'relates to the separation of coal from its impurities by the methods described in my United States Patents 1,224,138 and 1,392,401, now commonly known and hereinafter referred to as the sand flotation process. It especially relates to the removal from the fluid mass of fine material which will have a harmful effect upon the separating properties thereof. In Reissue Patent No. 16,674 various methods of dlscharging such fine material from the fluid mass are described and it is to the methods of operation and apparatus described therein that my present invention is particularly directed.

In the operation of the sand flotation process it is desirable that most of the finer coal be removed from the feed prior to its introduction into the separating fluid mass, as such fine coal of a size approaching that of the sand; grains of said fluid mass cannot readily be separated by said process. However it is diflicult to completely remove such finer coal from the feed and in addition a slight quantity thereofis produced by attrition during the operation of the process. It is therefore necessary to provide some means of removal and this has been accomplished by the use of fine screens, by separations that may be carried outhydraulically or by fluid mass flotation within the circuit, as disclosed in Reissue Patent No. 16,674, or by direct waste of some of the separatmg medium.

My present invention contemplates a diflerent method of operation of the general apparatus used for the circulation of the sand and water in said Reissue Patent No. 16,674,

the said apparatus being provided with certain adjunctive devices to permit such diflerence in method as illustrated by the accompanying drawing.

The drawing is a vertical elevation andpartial cross-section of the general association of elements that may be used with my invention, employing a separating receptacle of the type described in my United States Patent 1,559,937. It will be understood that said drawing is diagrammatic and in carrying out my lnvention I may employ any desired type of separating receptacle, and

means for removing the separated materials therefrom, that can be used for carrying out the sand flotation process.

The operation of my invention as shown by the drawing is as follows:

The raw coal to be cleaned is fed through chute 1 to fine coal screen surface 2 over which the material to be washed passes to separating receptacle 3, and through which the raw fines may be discharged to chute 2a. Said receptacle 3 is provided with refuse discharge valves 4, refuse chamber 5, refuse screen 6 and coal desanding and drainage screen 7. The washed coal passes over screen 7 to discharge chute 9 and the refuse over screen 6 to discharge chute 8, the sand and water recovered by these screens passing through conduit 10 to sand sump 11. The operation of this portion of the apparatus is similar to that of the apparatus described in United States Patent 1,559,937. My present invention has particularly to do with the sand sump 11. Said sand sump is provided with water overflow 12, sand return pipe 13, sand pump 14 and sand pump discharge-pipe 15, these latter elements serving to respectively discharge the substantially sand-free water from the upper portion of said sand sump and a thickened mixture of sand and water from the lower portion thereof, the latter being then returned by pump 14 to the separating receptacle.

Said water overflow 12 discharges into pump sump 16, to which is connected, by pump suction pipe 17, water pump 18, serving to return the circulating water required for agitation of the fluid mass, screen sprays and the like to the water circulating system. Sump 16 is provided with an overflow 2O fitted with atmospheric inlet 21, which may be constructed as shownin the drawing, to remove the overflow water from the lower part of said sump (thus retarding sedimentation therein while maintaining a constant level in the upper part thereof), siphoning being prevented by atmospheric inlet 21.

Make-up water, to replace that discharged by overflow 20 and otherwise lost from the circulating system is introduced by conduit with especial advantage under some conditions. It serves to maintain aconstant quantity of water in the circulating system and may consist in part of overflow water discharged by overflow 20 if suitable means are provided for removing the suspended solids from said overflow water after discharge through said overflow.

When coal is being washed by the apparatus, the total volume of water passing through screens 6 and 7 and conduit 10, to sand sump 11 consists of the sand pump water returned by pump 14 plus the extraneous water required for the operation of the sys tem, such as that used for agitation, shaker screen wash water, etc. This total volume, intermixed with the sand returned by pump 14: from sump 11 and such fine coal as passes said screens, passes out of the base of conduit 10, causing violent agitation in the lower part of sump 11, and divides into two portions, the extraneous water rising upwardly in said sump and the sand pump water discharging into said pump 14 by suction pipe 13.

By proper proportioning of the apparatus, much of said fine coal will be carried into the upper portion of said sump by said extraneous water, such fine coal as does not discharge through the overflow 12 remaining in maintained suspension in said upper portion. That which is not so carried up passes with the sand and sand pump water to pump 14 and thence back to receptacle 3.

The extraneous water passing out sand sump overflow 12, plus the make-up water introduced by conduit 22, discharges into sump 16 carrying with it such fine coal in suspension as is lifted out of said sand sump by said extraneous water, the remainder of the fine coal introduced by conduit 10 passing to the sand pump suction 13 or remaining suspended in sump 11 as aforesaid.

While some of the fine coal thus circulated may be removed by screening, hydraulic classification or other means nevertheless if the total removal so effected is less than the total input of such fine coal, the latter will accumulate in the circuit. In my present invention I retard such accumulation by continuously discharging a sufiicient quantity of mixed fine coal and liquid from overflow 20, the composition of such discharge being practically the same as that circulated by pump 18.

I have found that it is possible in this way to continuously circulate through pum 18 a mixture of fine coal and waterthat will contain no more fine coal than is permissible for the maintenance of the desired fluid mass in receptacle 3. It will be clear that if the quantity of fine coal so removed by overflow 20 plus any that may be otherwise removed, is as great as that entering the system through conduit 10 a condition of equilibrium as to the fine coal content will be reached. At

such equilibrium it is necessary that the fluid circulated by pump 18 shall not contain more fine coal than is desired this condition being attained by the volume passing out overflow 20, which is again controlled through the make-up water introduced by conduit 22.

It will be understood that a plurality of sand sumps may discharge to a single pump sump or that a plurality of such water sumps may be attached to a single sand sump, and that plural water pumps may be used with a common water sump 0r plural water sumps with a common water pump.

The drawing shows the general association of elements that may be employed with my invention, but it will be understood that the feed screen surface 2 is not a necessary adjunct to the operation of my present method.

While my invention is particularly designed for the cleaning of coal it will be understood that it may be applied to any materials separated by the processes described in said Patents 1,224,138 and 1,892,401, if said processes include circulation of portions of the separating medium.

By the term fluid mass I mean to include any mixture of comminuted solids and liquid which when properly agitated will approach the properties and fluidity of a true liquid; the term water is intended to mean any liquid suitable for making a fluid mass of the described type; and the term sand is intended to designate any comminuted solid, substantially insoluble in the liquid used and suitable for making a fluid mass of the described type.

By the expression fine coal or fine material I mean to include material which will have a harmful effect upon the separating properties of the fluid mass. In practice such material has been generally found to be that passing a round hole screen. The size of such material is governed by both the type of sand used as a solid component of the fluid mass and also by the characteristics of the material itself.

Having described my invention, I claim,

1. In separating materials of different specific gravities by immersion in a separatory fluid mass composed of an agitated mixture of liquid and comminuted solids substantially insoluble therein, said fluid mass being of specific gravity less than the heavier of said materials, in which a portion of said fluid mass removed with the materials separated thereby is first separated from the coarser of said materials, is then caused to fall commingled with smaller particles of the lighter separated materials and with liquid from a higher to lower elevation to maintain its fluidic properties, and is then returned to the se aratory fluid mass, and in which apart said commingled liquid is caused to flow upwardly through said fluidic fallen portion and transport smaller particles of said lighter materials to a zone remote from said fallen portion; the improved method which consists in causing said transporting liquid to assist in suspending said particles in said zone; in returning a ortion of said liquid admixed with some of said particles to said fluid mass; in discharging from said zone to without the separatory circuit, composed of said fluid mass, said removed portion and said zone, a volume of said liquid admixed with other of said particles; in addin to said separatory circuit a volume of liquld 'relatively free from such particles substantially equal to the total volume of liquid and particles so discharged; and in controlling the rate of such discharge of said particles, to approximate the rate at which like particles are introduced into said circuit with the coarser materials to be separated, whereby the proportion of such particles is prevented from rising above a predetermined maximum. in said circuit.

2. In separating coal from refuse by immersion in a separatory fluid mass composed of an agitated mixture of water and sand of specific gravity less than said refuse, in which a portion of said fluid mass removed with the coal and refuse separated thereby is first se arated from the coarser of said coal, is t en caused to fall commingled with the finer particles of said coal and with water from a higher to a lower elevation to maintain its fluidic properties, and is then returned to the separatory fluid mass, and in which a art of said commingled water is caused to ow upwardly through said fluidic fallen portion and transport fine particles of said coal to a zone remote from said fallen portion; the improved method.

4 which consists in causing said transporting water to assist in suspending said particles in said zone; in returning a ortion of said water admixed with some 0 said particles to said fluid mass; in discharging from said zone to without the separatory circuit composed of said fluid mass said removed portion and said zone, a volume of said water admixed with other of said particles; in adding to such separatory circuit a volume of water relav tively free from such particles substantially equal to the total volume of water and particles so discharged; and in controlling the rate of such discharge of said articles, to approximate the rate at which 11 e particles are introduced into said circuit with the coarser coal to be separated, whereby the roportion of such particles is prevented rom rising above a predetermined maximum in said circuit:

3. In apparatus for washing coal by the method of claim 2, in combination a container adapted to hold a fluid mass; a fluid mass consisting of an agitated mixture of sand and water contained therein; a secondary separating receptacle; means for circulating sand and water commingled with fine coal between said container and said receptacle; means for transporting portions of said fine coal substantially free from said sand to the upper part of said receptacle, said means comprising an upward current of said water; means for returning a portion of said transported fine coal and said transporting water to said fluid mass; means for returning sand and water from said receptacle to said container; means for discharging to waste outside of the circuit composed of said container, said receptacle and said circulating means a volume of said transported fine coal admixed with said transporting water; means for adding to said circuit a volume of water substantially equal to said volume of fine coal and water so discharged; and means for maintaining said transported fine coal in suspension prlor to said return and said discharge.

THOMAS M. CHANCE. 

